What software are you guy's using?

[Mithrandir]

I think I would be inclined to fatten this one up a little... as it is intended for low Rn

http://www.ae.uiuc.edu/m-selig/ads/afplots/s9032.gif

[esc]

Oops, sorry rcpilot82 I think you may have got the impression that I am thinking of changing the 3D plane - I am not. The aerofoils I am talking about at the moment are purely for my new design(s).

Spooky, I tried that with the 3D plane and was not 100% happy with the results. I have been taught how to adjust splines and test for, and adjust, curvature on complex shapes but it just seemed to me that if someone had gone to the trouble of generating a smooth shape using mathematics why approximate it with guess work?

Last night I had an email back from Stefano Duranti, the writer of Profili, and he assures me that his software generates very accurate DXF files. The price is much more reasonable than CompuFoil 3D, it is a complete program and the updates are free if you purchase the Pro version (40 Euros)

Dave.

[rcpilot82]

Ok, Just making sure before I cut parts.

[Spooky]

	Quote: Originally Posted by esc
	Spooky, I tried that with the 3D plane and was not 100% happy with the results. I have been taught how to adjust splines and test for, and adjust, curvature on complex shapes but it just seemed to me that if someone had gone to the trouble of generating a smooth shape using mathematics why approximate it with guess work? Dave.

I wasn't implying anything about your CAD knowledge or anything, just offering my own personal experience about that.... And it's not guess work if you trace or sketch over an existing airfoil... sure you can be off a few thousands of an inch, but does that really affect anything in flight on these models?... And when importing/exporting any universal type file (DXF, IGES) you loose integrity of that file around 2%, sometimes more, which usually shows up as misaligned edges, etc. , so right there your not getting that pure mathematical airfoil, but an interpretation of what the CAD program deciphers from that file, sometimes it's very close, sometimes not so.
Anyway, just throwing this out there as food for thought, and trying to save you 40 Euros...but if you feel that it's needed, don't let me influence your decision, just trying to help out is all....personally, I use 1 CAD program for everything I do and have been happy with the results, but that's me, everyone is different.

Anyway, good luck with the design and keep us posted.

regards,
Dean

[Mithrandir]

Profili has XFOIL embedded as well... you can do virtual wind tunnel analysis of airfoils

[esc]

Spooky,

Have I given you the impression that I was offended, if so I am sorry that was not my intention as I am definitely not. If I have offended you in anyway I apologise.

I do appreciate your suggestions, please keep them coming, I certainly don't profess to know it all - far from it.

One thing I must question though is this figure of 2% inaccuracy from DXF files - were did you get that from? I have never had inaccuracies in DXF files providing they were created properly in the first place.

I'll give you two examples I have come across over the years where this type of thing occured. I used to work with a guy who added bits of lines to the end of an existing ones to bridge gaps instead of using extend, fillet 0, etc. The same guy could have 42 or more of the same item stacked on top of each other and he never new how he did it! "Near enough is good enough" was his motto. Another guy I knew never used snaps to get end points, tangents, mid points etc he just eyeballed things on the screen and dropped lines in where he thought they conicided. These people are nightmares in the CAD world.

Enough of that, the real reason I called back was to say that I am starting a new thread in the CNC section on the Striker if you would care to drop in guys and leave your comments.

Regards,

Dave

[Spooky]

No problem esc, just throwing things out there, I'll try not to beat that dead horse anymore.

Anyway, I'm not a guru of CAD myself, heck, I don't even have a degree, and am pretty much self taught when it comes to CAD and engineering, with the exception of some CAD training courses and too many years in a machine shop. That 2% +/- loss was taught in every training course and from every instructor and engineer I've talked too and worked with, but since the DXF format was made by Autodesk, I'm sure their translator is geared towards it, which gives you a cleaner conversion. But, if you were to take the same DXF file and import it into either Pro-E or SolidWorks, the results would be different, it all depends on the translator. I used to use SurfCam's translator to convert files to input them into Unigraphics, a double convert, but it still came out better than what the UG translator would give you. I agree if the initial file is made correctly there's less loss of data when converted.

Here's an easy test to try, take a DXF and IGES file of the same part and convert it in Inventor (or any CAD program), then save it in it's native format (DWG or whichever it is), then compare their file size between the DXF/IGES and the native file and let me know what you get.

Just having some fun, don't take me too seriously, I get caught up in the details sometimes and rant on.

Look forward to your build thread,
Dean

[rcpilot82]

Dave,
I have been using ACAD since version 11 (dos) It is my profession, College education, and hobby. Though I also don't know everything ( I mostly do 2d work), I haven't heard my favorite command used yet. POLYLINE, I love em for things like airfoils and CNC files. I had to laugh as I was reading your post about people who dont use snaps, or overlay multiple lines. I work with a guy like this and I can't stand his drawings. Part of my duties are to make the CNC profiles for programming, anyone who has used a CNC knows if there is a break in the line or a step, it WILL show in the final product and cause problems while running the program. anyway, I am enjoying this thread and waiting on wood to start building. Could you post a link to the striker build thread here?

[Spooky]

Yep, I've worked with a couple guys that used to do that alot (broken lines), that's why I like working with solid models, you don't get that.

rcpilot82, this should look familiar, you being a CNC guy too, I was contracted to update their 2D drawings to 3D models and new drawings for them (Hint: Major tooling manufacturer). Here's a basic sample of an outdated product that was done some 8-9 years ago in Unigraphics. I've also done work for GM, Toyota, Pratt & Whitney (airfoil work) and assorted military and aerospace companies to name a few. That's basically my engineering background added to the 28+ years in various machine shops. So no degree, but some experience.

Guys, share some of your work or experiences here for others to check out, or maybe a problem your having for the collective to help solve.

Dean

[rcpilot82]

LOL, my guess is sandvick or kennametal CAT series holder?? am I close?

the more I look at it, I am leaning towards a DA collet holder

[Spooky]

	Quote: Originally Posted by rcpilot82
	LOL, my guess is sandvick or kennametal CAT series holder?? am I close? the more I look at it, I am leaning towards a DA collet holder

I think Kennametal bought out Sandvick, I could be wrong.
But yes, stock kennametal back-end used with pretty much that whole line of holders... Nice call

Dean

[esc]

Hi Guys,

Sure I'll give you the link to my new thread, here it is:

http://www.flyinggiants.com/forums/s...ad.php?t=44640

Talking about experience and degrees. I receive several professional engineering publications and in one of these I was reading an article about possible future advances. They talked about how knowledge was growing to such and extent more and more specialism will be required to handle it in smaller chunks. The writer also said that the average shelf life of a degree would be 6 months or less.

Frankly, although I am quite well qualified and a time served practical working engineer, I have always valued experience over book learning any day of the week. Book learning can go just so far and then it falls down.

A short story to illustrate my point: A company I worked for once employed a straight from University engineering graduate student.

She was asked to design a simple 19" rack mounting unit which as the name clearly suggests is basically a box mounted off a front panel in an electronic equipment rack.

This ex-graduate student designed her rack with the rear panel as large as the front so there was no way it could be fitted into a rack! She had totally missed the point despite having existing designs to copy, or modify, and the real thing available if she wanted to look at one.

Have a good weekend guys.

Dave

[rcpilot82]

Well, I got a box of wood today!! I have to say, I am very pleased with the look of this wood from rcfoam.com. I had to lauge cause there is a sticker on it that said it is "plantation grown balsa wood". never saw anything like that before! anyway, My goal is to have the wood cut by Wed. and start building as time permits. stay tuned.

[Spooky]

Cool rcpilot82... it's like Christmas in June for you.
I was wondering if you plan on starting a build thread or cutting/building her here?....either is cool by me, I'm just eager to see your CNC router in action.

Dean

[esc]

I can't wait - it's like giving birth (hopefully without the pain). Somebody pass the gas and air!

Dave